This application is related to concurrently filed application Ser. No. (876,232) entitled "Variable Control and Data Rates in Highly Efficient Multiplexer", which is hereby incorporated by reference herein and which is assigned to the assignee herein.
The present invention relates to time-division-multiplex (TDM) telecommunication systems which permit byte synchronization of apparatuses when bit interleaving of information is performed by the TDM system. More particularly, the present invention relates to systems for permitting byte synchronization for bit interleaved multiplexed information without consuming aggregate bandwidth beyond what is required for multiplexer framing synchronization.
In conventional bit interleaved TDM systems, where it is desired to transmit information, a transmit frame of the multiplexer comprises a memory means and a recirculating counter. The recirculating counter incrementally calls various addresses in the memory means. The memory means is programmed according to a framing algorithm to indicate which channel is to be polled for its information. When a channel is polled, it outputs a bit of information. Thus, binary information from different incoming channels are interleaved bit by bit by the multiplexer according to a framing algorithm for transmission. The multiplexed information is received at a receiving terminal where it is demultiplexed by a (de)multiplexer which has the framing algorithm information and which is synchronized with the transmitting multiplexer. In this manner, the stream of bits which was multiplexed together from a plurality of channels is divided into its composite parts and properly received by the terminals which are connected to the various channels. The multiplexed information typically includes data, control information, synchronizing information and intermultiplexer communication information.
Conventional TDM systems also include data buffers or elastic stores which are used to accommodate variances in the rate at which selects are sent to channels from the transmit and receive frames. The buffers absorb short-term variances in the rates at which data is selected by the frames and the rates at which data is sent to or taken from a terminal.
Because data and information are typically coded as bytes of information, it is desirable in TDM telecommunication systems for the receiving terminal to be aware of the location of the most significant bits (MSB's) of the received information. However, because the bytes are being sent bit by bit, the identification of the MSB's is not readily available. Some systems have overcome this problem by tagging the MSB (e.g. sending control or additional synchronizing information to accompany the MSB) so that it will be recognized by the receiving terminal. Other systems have sent additional address bits to indicate the start of each byte. While such schemes do overcome the problem, they have the unwanted effect of consuming valuable bandwidth thereby reducing data throughput. Clearly then, it would be advantageous to be able to locate the MSBs without using additional bandwidth.